This application claims the priority of application 197 19 791.4 filed in Germany of May 10, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a supporting disk for a supporting disk bearing of open-end spinning rotors, said disk comprising a tire (annular ring) with damping properties, which comprises an essentially cylindrical running surface limited by outer edges. The running surface is divided into sectional surfaces by endless grooves, extending in circumferential direction parallel to one another.
The annular ring, usually made of plastic, of supporting disks for high-speed open-end spinning rotors are also subjected, in addition to the mechanical load caused by the rotor shaft, to a high thermal load. Both types of load are contrary to one another, whereby with increasing width of the running surface, the thermal load increases and the mechanical load decreases. In order to reduce the thermal load, in practical machines the center of the running surfaces of the supporting disks are interrupted by a groove extending in circumferential direction.
U.S. Pat. No. 5,178,473 teaches that in addition to the centrically arranged groove, two further grooves are provided extending parallel to the central groove, so that the running surface is divided into two inner and two outer sectional surfaces. Thus the inner sectional surfaces located between two grooves are significantly wider than the outer sectional surfaces located respectively between a groove and an outer edge. Thus not only is the fact that the outer sectional surfaces are subjected to a higher mechanical load overlooked, but also thermal calculations show that the known arrangement of the grooves is in no way optimal with regard to avoiding heat build-up.
It is an object of the present invention to find a usable compromise for practical operation with regard to the thermal and mechanical loads of the supporting disks, thereby accommodating the thermal load, particularly dangerous for practical operation, by optimizing the arrangement of the grooves.
This object has been achieved in accordance with the present invention in that the running surface is interrupted by two grooves, thus dividing the running surface into one inner sectional surface located between the grooves and two outer sectional surfaces located between a groove and an outer edge respectively, and that each outer sectional surface is wider than the inner sectional surface.
Two grooves result firstly in the operational temperature of the running surface being lower than when only one single groove is present. The second groove also reduces the flexing work on the running surface, so that also in this respect a longer working life than that of supporting disks used in practical operation up to now can be expected. By means of the distribution of the sectional surfaces, as opposed to the above mentioned prior art, a significant reduction of the thermal load of the running surface also occurs. Calculations have shown that a relatively even distribution of temperature on the running surface can only than be achieved when the outer sectional surfaces are made wider than the inner sectional surface. One reason for this is that the running surfaces are cooled better during operation at the outer edges than in the area of the grooves. As the wider outer sectional surfaces are also favorable with regard to the mechanical load, the arrangement of the two grooves according to the present invention leads to a surprising result, namely that now the mechanical and thermal load are no longer contrary to one another, but rather that the arrangement of the present invention reduces the thermal and the mechanical load.
It has been established that the outer sectional surfaces may be 20 to 40% wider than the inner sectional surface according to preferred advantageous embodiments of the invention. In especially preferred advantageous embodiments, the tire or annular ring is made of a material with a hardness of Shore D between 49 and 55, and the width of the central portion between the two grooves is approximately 75% of the width of each of each of the outer sectional surfaces. Together the outer sectional surfaces may be wider than the inner sectional surface plus the two grooves, whereby for manufacturing reasons, the outer sectional surfaces can be made equally wide.
It is sufficient when the width of each groove is very small, the distance between the two outer edges should measure 10 times the width of one groove. The chosen width of the grooves lies between 0.7 mm and 1 mm, whereby the optimum lies around 0.8 mm. The width of the running surface between the outer edges lies advantageously between 7 and 10 mm.
The depth of the grooves need not be overly deep. The depth of the grooves is only slightly larger than their width, so that an almost square cross section arises, which may be rounded on the groove bottom. The grooves should have a depth which corresponds to a quarter of the thickness of the annular support ring. Rings with a thickness of 4 mm have been proven to be favorable. At this thickness, the damping properties of the annular support ring are still adequate, while the amount of plastic used is small.
In a further embodiment of the present invention, in particular in the case of somewhat wider running surfaces, the annular support ring in the area of the radial planes of the grooves can be additionally provided on its inner circumference with ribs, which engage in corresponding anchoring grooves of a disk-like base body of the supporting disk. The annular support ring is thus--as seen in cross section reinforced by ribs at those points where the grooves are located in the running surface. In the case of relatively narrow running surfaces the annular support ring may be affixed to a disk-like metal base body without any anchoring groove at all.
As the shaft, supported by the supporting disks, of an open-end spinning rotor in practical operation is disposed mostly at the outer edges of the supporting disks, the outer sectional surfaces can be advantageously bordered by small bevels in the area of the outer edges. The mechanical load is thus reduced at the particularly critical points of the outer edges.